I'm no RF expert by far, but I'll try my best. At that particular frequency where it has the highest absorbtion, it can absorb 99% of the reflected energy. I would assume they test at different frequencies and power levels to come to that conclusion. In our case, we picked this product since it had the highest absorbtion at the problematic frequency. We had a case where the product was passing certification, but the variant with coin cells sitting over the RF radiator did not. Placing the absorber on the RF module (below the coin cells) reduced the RSE levels enough to pass. We experimented with the different thicknesses and it was matching what the charts showed. We chose the 1mm since it allowed us to pass with a safe buffer.